U.S. patent number 6,723,099 [Application Number 10/035,515] was granted by the patent office on 2004-04-20 for three sided tack for bone fixation.
This patent grant is currently assigned to Biomet, Inc.. Invention is credited to David R. Goshert.
United States Patent |
6,723,099 |
Goshert |
April 20, 2004 |
**Please see images for:
( Certificate of Correction ) ** |
Three sided tack for bone fixation
Abstract
A surgical tack for bone fixation having a body portion with
barbs on the outside of the body portion to fixedly engage a bone
structure, and a head portion to assist in implantation of the
surgical tack. The tack also includes fins on the body portion to
reduce implantation forces while not reducing the holding power of
the surgical tack. The barbs extend from the fins to engage a bone
structure and increase the holding force of the surgical tack.
Additionally, a break-away portion is affixed to the head portion
to engage an implantation device to assist an implantation of the
surgical tack.
Inventors: |
Goshert; David R. (Pierceton,
IN) |
Assignee: |
Biomet, Inc. (Warsaw,
IN)
|
Family
ID: |
32067672 |
Appl.
No.: |
10/035,515 |
Filed: |
November 8, 2001 |
Current U.S.
Class: |
606/329;
606/75 |
Current CPC
Class: |
A61B
17/0642 (20130101); A61B 17/68 (20130101); A61B
2017/00004 (20130101); A61B 2017/0647 (20130101); A61B
2090/037 (20160201) |
Current International
Class: |
A61B
17/68 (20060101); A61B 17/064 (20060101); A61B
19/00 (20060101); A61B 17/00 (20060101); A61B
017/56 (); A61B 017/58 (); A61F 002/30 () |
Field of
Search: |
;606/61,65,70,72,73,75,76
;411/3,4,508,509,510,913,450,452,453,456,393,402,403,410 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Macropore .TM. Surgical Tacks and Drivers,
http:.backslash.www.macropore.com/prod04.htm, Nov. 7,
2001..
|
Primary Examiner: Robert; Eduardo C.
Assistant Examiner: Ramana; Anuradha
Attorney, Agent or Firm: Harness, Dickey & Pierce,
P.L.C.
Claims
What is claimed is:
1. A tack for fixation in bone, said tack comprising: a body
portion having a proximal end and a distal end, adapted to be
received in a bone structure; a head portion extending from said
proximal end of said body portion; a shearable member shearably
affixed to said head portion; and a projection having an exterior,
and operatively associated with said body portion to form a bone
engaging area, wherein said projection engages the bone structure
to hold said body portion in the bone structure; a fin having an
exterior, operably interconnecting said projection and said body
portion, wherein said projection extends from said exterior of said
fin.
2. The tack of claim 1, wherein said fin includes a plurality of
said fins.
3. The tack of claim 2, wherein said body portion and said fins are
integrally formed and have a generally triangular
cross-section.
4. The tack of claim 1, wherein said fin and said body portion are
integrally formed.
5. The tack of claim 1, wherein said body portion has a smaller
circumference at said distal end when compared to said proximal end
and has a generally tapered profile between said proximal end and
said distal end.
6. The tack of claim 1, wherein said projection is a barb having a
first end and a second end wherein said first end is near said
proximal end and said first end is larger than said second end.
7. The tack of claim 1, wherein said shearable member has a
substantially hexagonal cross section adapted to be received in a
tool.
8. The tack of claim 1, wherein said body portion, said head
portion, said shearable member, and said fin are all integrally
formed.
9. The tack of claim 1, wherein said tack is made from a
bio-compatible material selected from the group of a bio-absorbable
material, a titanium, stainless steel, and a ceramic.
10. A surgical fixation tack for use in orthopedic surgery, said
surgical fixation tack comprising: a tack portion having a first
circumference, a proximal end, and a distal end; a head portion
extending from lo said proximal end of said tack portion; and a
plurality of fins extending from said tack portion extending a
distance between said proximal end and said distal end, wherein
said fins have a second circumference greater than said first
circumference; and a member removably affixed to said head portion
opposite said tack portion; and a projection, wherein said
projection extends from at least one of said fins and is adapted to
increase the holding cower of said at least one fin; wherein said
tack portion, said head portion, said plurality of fins and said
member are substantially integrally formed.
11. The surgical fixation tack of claim 10, wherein said member
comprises a substantially hexagonal cross-section adapted to be
received within a tool.
12. The surgical fixation tack of claim 10, wherein said tack
portion has a smaller circumference at said distal end when
compared to said proximal end and has a generally tapered profile
between said proximal end and said distal end.
13. The surgical fixation tack of claim 10, wherein said at least
one fin includes a plurality of said projections, wherein a profile
of said of at least one fin is stepped.
14. The surgical fixation tack of claim 10, further comprising a
body, wherein said tack portion is generally cylindrical and said
fins project a distance from said tack portion to form said
body.
15. The surgical fixation tack of claim 14, wherein said body has a
generally triangular cross section.
16. The surgical fixation tack of claim 10, wherein said tack is
formed of a bio-compatible material.
17. A surgical tack for orthopedic implant adapted to be held in a
structure defining a bore having a bore circumference, said
surgical tack comprising: a tack portion having a proximal end and
a distal end and adapted to be held in the structure defining the
bore; a plurality of fins extending from said lack portion; a head
portion extending from said proximal end of said tack portion; and
a projection extending radially from at least one of said plurality
of fins, wherein said projection is adapted to hold said tack
portion in the bore, wherein said projection is a barb having a
first end and a second end wherein said first end is nearer said
proximal end than said second end and said first end is larger than
said second end.
18. The surgical tack of claim 17, wherein said tack portion
includes an internal circumference and said fins form a first
external circumference, wherein said first external circumference
is adapted to be less than the bore circumference.
19. The surgical tack of claim 18, wherein said projection forms a
second external circumference greater than said first external
circumference, wherein said second external circumference is
adapted to be greater than the bore circumference.
20. The surgical tack of claim 19, wherein said projection is
integrally formed on said fin.
21. The surgical tack of claim 17, further comprising a removable
member removably affixed to said head portion, wherein said
removable member comprises a generally hexagonal cross section
adapted to be received in a tool.
Description
FIELD OF THE INVENTION
The present invention relates generally to bone fixation devices
and more particularly to bone fixation push pins or tacks.
BACKGROUND OF THE INVENTION
Bone structures in a human body, or other animals, may undergo
degenerative processes which lead to weakening or an ultimate break
of the bone structure. Additionally, a catastrophic event may cause
a break or fracture in the bone structure. When such breaks occur,
some kind of repair mechanism must generally be used to help the
bone heal properly. Certain mechanisms include external fixation of
the bone structure so that it can grow together in proper
alignment. External fixation is fixation of the bone structure with
a device placed on the outside of the derma. Other methods include
internal fixation which include some mechanism placed subcutaneous
to hold the bone structure in place while it heals.
Internal plate and bone fixation methods are generally known.
Plates having a specific rigidity are mounted to bone structures
using known fixture means. One known method of fixing a plate to a
bone is using a surgical screw which is held in place through
threads. These screws are inserted using a driver into a pilot hole
that had been drilled into the bone. Additionally, surgical or
orthopedic tacks are known to hold bone plates,in place. The tack
is press fit into a pilot hole that was drilled into the bone
structure. Generally, these bone tacks resemble hardware tacks.
Known tacks generally included a head portion affixed to a proximal
end of a tack body. The tack body has a generally sloping profile
that terminates in a sharp point or relatively narrow distal end.
These tacks may also include ribs that help hold the tack in place.
Generally, however, the pilot hole for these tacks must be
substantially equal to the greatest diameter of the tack body. If
the pilot hole is not substantially equal to the width or diameter
of the largest part of the tack body, great pressure must be used
to insert the bone tack into the bone and hold it in place.
It is, therefore, desirable to have a bone tack that has an
increased holding power without requiring the increased pressure to
implant the bone tack into the bone structure. It is also desirable
to decrease the resulting stress on the bone structure after
implantation. When additional force is used to push a bone tack
into a bone structure, greater trauma may arise than if a smaller
force was used to insert a bone tack into the bone structure.
SUMMARY OF THE INVENTION
A first embodiment of the present invention includes a bone
fixation tack which has a body which has a proximal end and a
distal end wherein the tack is to be received in a bone structure.
A head portion extends from the proximal end of the body. A
removable member further extends from the head portion. Finally, a
projection is operatively associated with the body portion to form
a bone engaging area when implanted in the bone structure.
A second embodiment of the present invention includes a surgical
fixation tack which has a tack portion having a first circumference
and a proximal end and a distal end. A head portion extends from
the proximal end of the tack portion. Finally, a plurality of fins
extend from the tack portion and form a second circumference which
is greater than the first circumference.
A third embodiment of the present invention includes a surgical
tack that has a tack portion with a plurality of fins where the
fins effectively reduce the surface area of the tack portion. A
head portion extends from the tack portion. Finally, projections
are operatively associated with the tack portion to help hold the
tack portion in the structure.
The bone fixation tack according to the present invention has a
generally circular interior cross section with a generally
triangular total cross section. The triangular cross section
provides a minimal resistance during the implantation of the bone
fixation tack into a bone structure. After implantation, each point
of the generally triangular cross section will provide resistance
to extraction or unintended removal of the bone fixation tack from
the bone structure into which it was implanted. Additionally,
projections, such as barbs are formed on each of the points of the
triangular cross section to also resist removal of the bone
fixation tack. The head portion of the tack may also include an
integrally formed insertion member which may be removed once the
bone fixation tack has been affixed into the bone. Also, a plate
through which the bone fixation tack will be inserted is disclosed
to hold two portions of the bone relative to each other for a
healing process.
Further areas of applicability of the present invention will become
apparent from the detailed description provided hereinafter. It
should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the
detailed description and the accompanying drawings, wherein:
FIG. 1 shows an elevational, view of a bone fixation tack including
a break-off hex according to a first embodiment of the present
invention;
FIG. 1a shows a perspective view of the bone fixation tack of FIG.
1;
FIG. 2 shows a cross-sectional view taken along line 2--2 of FIG.
1;
FIG. 3 is an exploded view of the insertion of a bone fixation tack
into a bone structure through a bone plate according to a first
embodiment of the present invention;
FIG. 4 is a elevational view of a bone fixation tack insertion
instrument engaging a bone insertion tack through a bone fixation
plate and bone structure according to the first embodiment of the
present invention;
FIG. 4a is a detailed view of FIG. 4 taken about circle 4a;
FIG. 5 is a side elevational view of a bone fixation tack according
to a second embodiment of the present invention;
FIG. 6 is a side elevational view of a bone fixation tack according
to a third embodiment of the present invention; and
FIG. 6a is a cross-sectional view taken along lines 6a--6a of FIG.
6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiment(s) is merely
exemplary in nature and is in no way intended to limit the
invention, its application, or uses. Additionally, exemplary
measurements and ratios are given without intending to be bound to
the specific measurements given and described.
With reference to FIGS. 1 and 1a, a first embodiment of a bone
fixation device 10 is shown including a bone fixation tack 12 and a
break-off hex driver 14. The bone fixation tack 12 includes a head
portion 16 and a tack or body portion 18 where the body portion 18
is to be implanted into a bone structure of a patient. The body
portion 18 has a proximal end 18a near head portion 16 and a distal
end 18b. Break-off hex 14 includes a snap or break-away region 20
that is formed to be weaker than the surrounding area to facilitate
the removal of the break-off hex 14 after the bone fixation tack 12
is implanted into the bone structure. The break-away region 20
extends between the break-off hex 14 and the head portion 16 and
holds the bone fixation tack 12 to the break-off hex 14 during
implantation of the bone fixation tack 12.
The head portion 16 includes an annular bottom surface 22 which is
to be received into a bone fixation plate (shown at 54 in FIG. 3)
for a flush fit with the bone fixation plate 54. The head portion
16 also includes a top surface 24 which is adapted to lie
substantially flush with the bone fixation plate 54 once inserted.
Directly below the bottom surface 22 is a collar region 26 which
extends between the body portion 18 of the bone fixation tack 12 to
the head portion 16. The collar region 26 gradually increases in
diameter from the diameter of the body portion 18 to a diameter
slightly less than the diameter of the head portion 16. This
ensures a strong fixation between the body portion 18 and the head
portion 16 of bone fixation tack 12.
Extending from the collar region 26 is a top or top portion 28 of
the body portion 18. With continuing reference to FIG. 1 and
further reference to FIG. 2, the body portion 18 includes a central
region 30 and fins 32. Fins 32 are substantially equal to or
greater than diameter to the top portion 28. Central region 30
includes a center point A and is generally circular having a radius
B. For example, the radius B between center point A and interior
edge 34 may be between about 0.01 and about 0.5 inches. A second
radius or distance C is formed from center point A to an outside
edge 36 of each fin 32. An exemplary length of distance C may be
about 0.01 inches to about 1.0 inches. This configuration defines
an inner circumference D, defined by radius B, smaller than an
exterior circumference F, defined by distance C. It will be
understood that the distance of radii B and C are exemplary only
and may be any appropriate length depending upon the intended
application.
Body portion 18 may be formed in several different ways. One
method, for exemplary purpose only, is that fins 32 may be affixed
to the central region 30. A circular central region, having
substantially parallel sides such as a cylinder, may have affixed
to it through a suitable means, such as welding, the fins 32. A
second example of forming the body portion 18 is to view the
central region 30 as an imaginary portion simply defining a central
continuous circumference inside of fins 32. Such a structure is
formed through providing a substantially cylindrical portion having
a radius substantially equal to the distance C and grinding down
three sides of the cylindrical portion. Grinding down three sides
would produce the fins 32 and the body portion 18 having a
generally triangular a cross section. Central region 30 would still
be defined by a circumference with the radius being substantially
defined by the distance B.
Each fin 32 also includes a projection or barb 38. The barbs 38
project and are formed on the outside edge 36 of fins 32. Barbs 38
resist the tendency of the bone fixation tack 12 to move backward
out of a pilot hole formed in the bone structure. Barbs 38 have a
distance from center point A greater than or equal to the distance
C the outside edge of fins 32. Barbs 38 also include a structure to
assist in implantation of the bone fixation tack 12 while resisting
the removal of the fixation tack 12. In particular, a proximal edge
38a of the barb 38 nearest the proximal end 18a of the body portion
18 has a height above the fin 32 greater than a distal edge 38b of
the barb 38, which is closest the distal end 18b of the body
portion 18. In particular, the proximal edge 38a of the barb 38
would define radius C', the greatest radius of the body portion 18.
Furthermore, an outer surface 38c of the barb 38 has an incline
from the proximal edge 38a to the distal edge 38b. The proximal
edge 38a has a height of about 0.001 inches to about 0.01 inches
above the outside edge 36 of fin 32 which, for example, is about
0.001 inches to about 0.01 inches greater than distance C. The
distal edge 38b is substantially planar with the outside edge 36 of
fin 32, or a distance equal to distance C. Therefore, surface 38c
would assist in the implantation of the bone fixation tack 12 while
the proximal edge 38a will resist the removal of bone fixation tack
12.
Distal end 18b of the body portion 18 is narrower and has a smaller
diameter than the top portion 28. A plane 40 parallel to center
point A forms an angle of .theta. approximately 12-18 degrees from
the outside edge 36 of fin 32. Angle .theta. allows the distal end
18b to be more easily implanted into the bone structure. This helps
decrease the force necessary to begin the implantation of the bone
fixation tack 12 into a surface. The distances C and C' may also
increase from the distal end 18b to the proximal end 18a of the
tack body 18 such that the fins 32 are sloped from the distal end
18b to the proximal end 18a, as are the barbs 38.
With continuing reference to FIG. 2 and to FIG. 3, an exploded view
of the process of implanting bone fixation tack 12 is illustrated.
A pilot hole 50 is first formed in the bone structure 52 to receive
the bone fixation tack 12. The bone fixation tack 12 is then driven
through a bone fixation plate 54 and into the pilot hole 50. A
driver 56 having a first end 56a engages the break-off hex 14 to
help hold bone fixation tack 12 during implantation. A bore 58 is
formed in the bone fixation plate 54 to receive the bone fixation
tack 12. Additionally, an upper surface 60 of the bone fixation
plate 54 includes a recess 62 adapted to substantially receive
bottom surface 22 of head portion 16. Pilot hole 50 has a radius 64
in between the length of radius B and radius C.
The bone fixation tack 12 has a first circumference or first
effective circumference D which is the circumference of the
internal area 30. The bone fixation tack 12 also has a second or
outer circumference F defined by radius C which is the distance
between the center point A and the outer surface 36 of each fin 32.
It will be understood that other gradually increasing outer radii
will be formed by the outer surface 38c of each barb 38. Pilot hole
50 may be any circumference between inner circumference D and outer
circumference F. This allows for an engagement between fins 32 and
the bone structure 52 while not requiring every portion of the
outer surface of the bone fixation tack 12 to engage the bone
structure 52. Implantation forces are substantially reduced when
pilot hole 50 has a radius in between distance C and distance C'.
Additionally, implantation forces, while maintaining an acceptable
holding force, are optimized when the radius of the pilot hole 50
is, for example, between about 0.001 inches and 0.01 inches less
than distance C'. With particular reference to FIG. 2, shaded areas
65 are defined by the area of the fin 32 between the radius 64 of
the pilot hole 50 and the distance of radius C or outer
circumference F. The bone engagement area 65 is the primary or only
area of the bone fixation tack 12 that actually engages the bone
structure 52 during implantation of the bone fixation tack 12. It
will also be understood that barbs 38 extending from outer edge 36
of fin 32 are also engaging bone structure 52 and further resist
removal of the bone fixation tack 12 due to the inverted incline of
outer surface 38c. It will also be understood that the area of the
bone engaging area 65 may be increased or decreased by altering the
radius 64 of the pilot hole 50.
Turning to FIGS. 4 and 4a, bone fixation tack 12 is shown implanted
into a bone structure 52. Driver 56 engages the break-off hex 14 of
the bone fixation device 10 prior to breaking away the break-off
hex 14. A hexagonal design of the break-off hex 14 ensures a tight
fit of bone fixation device 10 with the driver 56. Also, the
hexagonal design of the break-off hex 14 ensures that torque may be
transmitted between the driver 56 and the bone fixation device 10.
The bone fixation tack 12 is fit through the bone fixation plate 54
and into the bone structure 52. Head portion 16 is substantially
received into the recess 62 of the bone fixation plate 54 to ensure
that a profile over the bone fixation plate 54 is substantially
flat so as to reduce irritation to the patient after implantation.
Additionally, barbs 38 engage the bone structure 52 after
implantation into the bone structure 52. Since the radius 64 of the
pilot hole 50 is between distance C and distance C', only the
portion of the barb 38 near the proximal edge 38a engages the bone
structure 52. With particular reference to FIG. 4a, the bone
fixation tack 12 is held in the bone structure 52 with a portion of
the barb 38. The portion of the barb 38 between line G and the
proximal edge 38a engages the bone structure 52. For example, this
area may be represent about the upper forty percent of the barb
38.
Implantation of the bone fixation tack 12 into the bone structure
52 is generally achieved by pressing the bone fixation tack 12 in
through the bone fixation plate 54 into the bone structure 52. Bone
fixation device 10 is first placed in driver device 56 and held in
place with the driver break-off hex 14. Pilot hole 50 is formed
into the bone structure 52 using any suitable means. The surgeon
then presses the bone fixation tack 12 into bone structure 52
through the bone fixation plate 54.
Since the radius 64 of the pilot hole 50 is less than radius C of
the body portion 18, a certain amount of force is needed to press
the bone fixation tack 12 into the pilot hole 50. Since only three
bone engagement areas 65 of the fins 32, have a distance
substantially greater than the radius 64 of the pilot hole 50, the
force which is necessary to implant the bone fixation tack 12 into
the bone structure 52 is reduced as compared to if the entire body
portion 18 had an equal radius. Due to the bone engagement areas 65
of fins 32, the surface area engaging the bone structure 52 in the
pilot hole 50 is less than if the entirety of diameter F were
filled with the bone fixation tack 12. Due to the presence of fins
32, only the area bounding the outside of the bone engagement area
65 engages pilot hole 50 during implantation of bone fixation tack
12. Therefore, the effective contact surface area of the bone
fixation tack 12 is reduced due to the presence of fins 32 and the
corresponding bone engagement areas 65. Thus, the force necessary
to implant the bone fixation tack 12 is reduced when compared to a
tack not including fins 32 and respective bone engagement areas
65.
Though the presence of fins 32 may decrease the surface area
engaging the pilot hole, 50 during implantation, the holding force
of the bone fixation tack 12 is not substantially reduced. Barbs 38
help ensure a strong and firm interaction of the bone fixation tack
12 and the bone structure 52. Not only do the fins 32 themselves
engage the bone structure 52, but also the barbs 38 have additional
surface area to engage the bone structure 52.
Both pull out and shear force tests were performed on a bone
fixation tack according to the first embodiment of the present
invention made formed according to the present invention of
LactoSorb.RTM., a material available from Biomet, Inc. in Warsaw,
Ind., and trauma screws. As a result of these tests, it was found
that bone fixation tack according to the present invention perform
substantially as well as screws under similar conditions.
Furthermore, the fact that the bone fixation tacks can be implanted
approximately six times faster than trauma screws may greatly help
in emergency situations. Additionally, the equivalency of the two
systems can help ensure that the speediest alternative may be used
without concern for the ability of the bone fixation tack to
perform its task.
With reference to FIG. 5, a second embodiment of a bone fixation
tack 70 is shown. Similar structures are given similar reference
numerals here as described above in relation to the first
embodiment augmented with a prime designation. According to the
second embodiment of the second invention, a bone fixation tack 70
is substantially similar to the fixation tack 12 as described in
the embodiment of the present invention. Bone fixation tack 70,
however, does not include a break away hex 14 affixed to the head
portion 16. However, bone fixation tack 70 does include a head
portion 16' and a body portion 18'. Body portion 18' includes
several portions also described above in relation to the first
embodiment of the present invention and not repeated here.
According to the second embodiment, a different driver would be
necessary. However, overall bulk of bone fixation tack 70 is less
than the first embodiment of the present invention and may reduce
production costs. Furthermore, other types of devices may be used
to implant bone fixation tack 70 by providing particular designs or
detents in the head portion 16' of bone fixation tack 70.
With reference to FIGS. 6 and 6a a bone fixation device 80,
according to a third embodiment of the present invention is shown
where similar portions are given similar numerals augmented by
double primes as those described, in the first embodiment of the
present invention. Bone fixation device 80 includes a head portion
16" and a body or body portion 82. The body portion 82 includes
four fins 84 rather than three as illustrated in reference to a
first embodiment of the present invention. The central region 30"
includes a center point A" and a distance B" between the center
point A" and an outside edge 34" of the center region 30". A
distance C" between center point A" and outside 36" of fin 84 may
be equal to distance C or may vary therefrom. Providing four fins
84 simply increases the surface area which, may engage a pilot hole
formed in the bone structure. It will also be understood that
additional fins may be formed on a bone fixation tack in a number
greater than four as well without departing from the scope of the
present invention. However, as a greater number of fins are added,
there is a corresponding increase in implantation force.
The bone fixation tack of the present invention may be formed of
several materials. One embodiment provides making the bone fixation
tack from LactoSorb.RTM., which is a bio-absorbable material, or
other bio-absorbable material. LactoSorb.RTM. includes L-lactic
acid and poly glycolic acid in combination to form a substantially
solid material. The LactoSorb.RTM. or similar materials are
absorbable into the body after the bone fixation tack has been
implanted and the bone structure has had time to heal. However, it
will be understood that bone fixation tack may be formed of any
bio-compatible material including titanium, stainless steel, or
other metal alloys that have sufficient strength and rigidity to
hold a bone structure during healing.
The description of the invention is merely exemplary in nature and,
thus, variations that do not depart from the gist of the invention
are intended to be within the scope of the invention. Such
variations are not to be regarded as. a departure from the spirit
and scope of the invention.
* * * * *